To use an overworked real estate term, the house at 77 Prof. Dondersstraat, a tree-lined thoroughfare in the Dutch city of Tilburg, had “good bones.”

Built in 1927, the spacious home was designed in the “Hague Style,” a restrained interpretation of Art Deco characterized by strong lines. It had oak and mahogany parquet floors and oak shutters. Its leaded glass windows resembled the work of the Dutch painter Piet Mondrian in the 1920s—geometric designs composed of straight vertical and horizontal lines with only a few spots of color. The dining room opened onto a terrace and garden.

But the house was more than 70 years old and in disrepair when historian Arnoud-Jan Bijsterveld and his spouse, anesthesiologist Hans Harbers, bought it in 2000. As they prepared to update their home, the couple obtained a copy of the original building plans from the municipality of Tilburg. Bijsterveld couldn’t help but notice the name of the original owner in one corner: M.H. Polak.

For Bijsterveld, the name was the starting point of a quest. He knew that Polak was one of the most common Jewish family names in the Netherlands. He wondered what had been the fate of the Jews who had eaten in his dining room and enjoyed a view of the garden from his terrace? Did they perish in the Holocaust, as did more than two-thirds of the 140,000 Jews living in the Netherlands in 1940? If the house had been seized by the Nazis, had the Polak family been fully compensated after the war?

As a historian born and raised in the Netherlands, he had to find out. His research culminated in the publication last December of the aptly titled book “House of Memories: Uncovering the Past of a Dutch Jewish Family.” He might have added a subtitle—“and the Present”—as he has also reached out to surviving family members and their descendants.

“What’s unusual is that this man wrote a book,” says Judith Gerson, a Holocaust scholar at Rutgers University. “There are many published memoirs of the Holocaust that are family histories. But the fact that the author is able to place the story in the house and use the house as a vehicle to tell the story, that strikes me as exceptional.”

Explains Bijsterveld, 55: “The history of the Dutch Jews has been part of my upbringing. My grandparents spoke a lot about their war experience.” His late mother talked about a kindergarten classmate in her convent-run school—a Jewish girl who, to evade the Nazis, assumed a new name and identity. “This is not just the Anne Frank story. It’s wider.”

Bijsterveld is a medievalist, not a Holocaust scholar, so he turned to his colleagues for help in tracking down information about the family. One, Jan Bader, was writing a book about the history of Jewish cemeteries in the region. It turns out that Bader had studied the life of Alfred Polak, a Zionist in Tilburg who was the brother of Max Henri “Hans” Polak, the man whose name Bijsterveld had noticed on the house plans. The men were partners in a leather hides company.

Bader told him that the Polak families had escaped to New York in 1940 and suggested he talk with Ernst Elzas, one of the few Jews still living in Tilburg after the war, which he survived by going into hiding.

It turned out that Elzas had gone to school with Bertram Polak, the popular only son and eldest child of Hans Polak and his wife Bertha. From Elzas, Bijsterveld learned that Bertram had been killed at Auschwitz-Birkenau in 1942. He was 24. He had been separated from his family because of his military service, and, when he returned home in May 1940, he found a vacant house. He tried to escape with three friends, but they were all betrayed and murdered.

Bijsterveld met Elzas in 2003. He found more information about Bertram in the central database of Shoah victims at Yad Vashem, but his attempts to locate and connect with surviving family members were unsuccessful. In 2005, he put aside his search.

His interest was rekindled in 2010—the year Elzas died—when the first “stumbling stones” were laid in Tilburg. The bronze stumbling stones, embedded in front of homes formerly occupied by Jews, serve as individual memorials to Holocaust victims.

“When I embarked on my search for the Polak family... I feared that not much would be left in the sense of living memories and material documents and objects,” 70 years after the Polaks had left the Netherlands, he writes in the prologue of his book. “What and who could be left to know who these people had been, what had happened to them, and how their lives had been before, during, and after the Holocaust?”

Medievalist Meets Genealogist

Enter Steve Jaron, 38, who lives in his native Pittsburgh. He became interested in family history at age 13 on his first trip to Israel, where he met relatives of his maternal grandmother, Judith Rothstein-Polak. An assignment for a college class to make a family tree led him to explore his ancestry.

In September 2010, he noticed that someone named Arnoud-Jan Bijsterveld had recently posted information on an online profile of Bertram Polak, his grandmother’s first cousin. The profile was part of a website called the Joods (Jewish) Monument, maintained by Amsterdam’s Jewish Cultural Quarter, which includes the Jewish Historical Museum and the National Holocaust Museum.

The Joods Monument is a digital tribute to the more than 104,000 Dutch Jews who were persecuted and died during the Holocaust.

Jaron wondered whether this Bijsterveld fellow might be a long-lost relative. They exchanged emails, and the genealogist introduced the historian to the rest of his family. That included his grandmother Judith and her two older sisters, Adah Cohn-Polak and Edith Spitz-Polak, who had made aliyah after fleeing the Netherlands with their parents, Alfred and Fien. The sisters had lived with their parents two doors down from Bertram’s family and immigrated to Israel. “I was very close to my uncle’s family,” recalls Judith, a sharp 93-year-old widow who lives in Pittsburgh. “They were like sisters and a brother. We were in and out of each other’s houses.”

Jaron also put Bijsterveld in touch with his great aunt Constance “Connie” Victor-Polak, Bertram’s half-sister, the only child of Hans Polak and his second wife, Charlotte Elias, more than 20 years his junior. Connie, who now lives in Philadelphia, was born in New York in 1941, when her father was 53.

“From very early on, I knew that they had escaped. I knew there had to be relatives somewhere,” Bijsterveld says of Bertram’s family. “It was only after Steve Jaron contacted me that I found out there were so many relatives. It was very overwhelming. As a medievalist, you never experience the people you research. From the very first moment, they allowed me to ask everything. “

Of course, as Judith’s sister Adah told him, “We first checked you out on the Internet.”

Bertram’s relatives were full of questions. “Sometimes it’s easier if an outsider starts to do the research,” Bijsterveld says. “I’m really grateful to this family. They allowed me to do that, and they shared anything they knew.”

Connie Victor-Polak calls Bijsterveld “a blessing.” “This is his field, history, so he knows how to research. We’ve been very fortunate in that the cousins who lived through this all have very sharp minds with great memories of details.”

Hans died at age 54 in 1942, when Connie was only a year old. “My supposition is that he died of a broken heart. Obviously, father must have been very close to Bertram. He was the prince of the family. My father apparently sent [Bertram] money and a ticket for a ship from London to America, and that ticket was returned.” That must have been when her father’s worst fears about his son were realized, she said. Connie’s mother never remarried. She died in 1991 at the age of 80.

No one talked about Bertram when Connie was growing up. She didn’t learn about him until she was a teenager and one of her sisters mentioned him. He would have been more than 20 years older than she was. The next-born, Connie’s sister Florentine, was three years younger than Bertram, and their twin sisters, Louise and Leonie, were two years younger than Florentine. Louise and Leonie died of heart disease at age 45 and 32, respectively.

Beri Kravitz, the youngest of Judith’s three daughters, was always surprised by her mother’s and aunts’ lack of bitterness about their war experiences. “She would talk more about, oh, this is what it was like in school, or this is how we celebrated the holidays. Kind of the fond memories. A little bit melancholy, but never bitter. I don’t understand how they could be like that.”

But then the 52-year-old Kravitz, a mother of four who lives in suburban Washington, D.C., answers her own question. “The story that we always grew up with, the narrative of our family, is we were so fortunate. We have this huge family in Israel. We really survived this largely intact.”

After the war, ownership of the houses of the late Hans Polak and his brother, Alfred Polak, was rapidly restored to their families. Both houses had been rented out to help solve the severe housing shortage. In 1947, Alfred and his wife, Fien, moved back into their home at 73 Prof. Dondersstraat. They remained there until Alfred’s death in 1956, at 72, after which Fien joined Adah and Edith and their families in Israel.

As soon as he realized that a Jewish family had built his home, Bijsterveld bought a mezuzah to attach near the front door. Given that the family’s name was Polak, he selected a replica of a 19th-century Polish mezuzah from New York’s Jewish Museum. “There is no scroll in it, to symbolize that the Jewish identity was no longer there,” Bijsterveld says.

A mezuzah wasn’t enough, though. Even before he found Bertram’s family, he began investigating what it would take to get a stumbling stone installed in the brick sidewalk in front of his house to memorialize the young man.

Stumbling stones, or “Stolpersteine,” were conceived by a non-Jewish German artist named Gunter Demnig to honor anyone, Jewish or not, who was persecuted or murdered by the Nazis between 1933 and 1945. The name of the mini-monuments reportedly refers to an anti-Semitic German saying that predates the Holocaust. When a non-Jew stumbled on a protruding stone, he or she would say, “a Jew was probably buried here.”

Each 4-inch-square stone bears a brass plate with the heading “Here Lived” and an individual’s name; birth year; date of arrest, if applicable; the name of the camp in which they were detained; the year in which they were deported to a concentration camp; and the date of their murder. The stones are usually placed in the sidewalk in front of the last place the individual lived by choice. More than 60,000 stumbling stones have been laid in more than 1,800 places in 21 countries.

Florentine Piel-Polak, the oldest of Hans Polak’s daughters, died eight days before the April 2011 ceremony marking the installation of Bertram’s stumbling stone in front of 77 Prof. Dondersstraat. Florentine was nearly 90 and suffered from Alzheimer’s, so she did not know about the Dutch historian who worked so hard to help preserve the memory of her older brother.

Bertram’s stumbling stone was laid by his nephew, Alfred “Fred” Piel, Florentine’s only child, assisted by two of his Aunt Connie’s grandchildren. The ceremony marked the first time the 62-year-old Fred, an internist in Springfield, Mass., had ever met his mother’s cousins or any of their children or grandchildren. And before that trip to Tilburg, he had met Judith only once, when he was a child.

“Both my wife and I were just totally entranced with these three women,” Fred recalls, noting that he felt “an instant connection” with them and their families, as he did with Bijsterveld and Harbers, his spouse. Bijsterveld’s research into the Polak family, leading up to the stumbling stone ceremony for Bertram, was documented in a 2012 short Dutch film called “Here Was Bertram,” which can be viewed on YouTube.

Florentine had fallen out of touch with her cousins after marrying Fred’s father, Kurt Piel, a non-Jewish native of Germany who immigrated to the United States in 1929 and worked as a barkeeper. “Although she always identified as a Jew culturally, she stopped identifying as a Jew religiously,” says Fred, who was baptized as a baby and confirmed in the Congregational Church when he was 13. While Florentine was their only Jewish grandparent, two of Fred’s three sons have taken Birthright trips to Israel.

Fred’s father served in the U.S. Army during the war, while his paternal grandfather was a German soldier. “In some ways, I’m obsessed by the war in Europe. Half of my family was doing these horrible things to the other half of my family. It was always very much in my mind that I had this uncle whowas killed.”

As the years pass, fewer remember the flesh-and-blood Bertram, the young man who preferred sports to books and named his dog “Tarzan.” His cousin Edith suffered a stroke in December 2015 and died two days later. Adah’s husband, Alfred Cohn, had survived the Monowitz concentration camp; he died last November at 95.

To make sure that Polak descendants will be able to read about their ancestors, Bijsterveld wrote “House of Memories” in English, although he plans to write an abridged version in Dutch.

The original English version is more than 600 heavily footnoted pages long and filled with photos. “At some point, you really have to say stop, and I reached that point about a year and a half ago,” Bijsterveld says. “This will be the book that will end up on all the relatives’ bookshelves. This has to include everything.”